Bryan, I will guess you are wondering about the overall output of the sub's amp and how much SPL increase there is going from minimum to maximum, trying to see if this amp is up to specs or not. I don't know the answer, as yours was my first and only EP500 experience.
Like the others have said, turn up the receiver output and drop the volume on the sub's amp, no problems this way. I have my sub's volume control near minimum and the receiver output at -5.